1. Field of the Invention
The present invention relates to a liquid discharge head and an image recording apparatus, and more particularly to temperature adjustment in a liquid ejection head.
2. Description of the Related Art
An inkjet head (recording head) has a composition in which ink is supplied to pressure chambers connected to nozzles, and liquid droplets are ejected from the nozzles by applying a pressure change to the liquid inside the pressure chambers. If there is an air bubble inside a pressure chamber, the pressure required for ejection is not transmitted to the ink, and an ejection error thereby arises. In order to prevent ejection errors of this kind, an operation is performed in order to suction the ink containing air bubbles inside the pressure chambers and expel the air bubbles together with the ink (namely, a “suction operation”). However, there is a problem in that the amount of ink consumed increases when a suction operation is performed.
Japanese Patent Application Publication No. 2001-146012 discloses an inkjet head, in which a thermoelectric element unit having a plurality of Peltier elements is disposed in a position opposing the pressure generating chamber, on the other side of the base plate of the pressure generating chamber. When this thermoelectric unit is operated, the base plate of the pressure generating chamber is cooled and hence the ink inside the pressure generating chamber is cooled as this base plate is cooled. By cooling the ink, it is possible to increase the solubility of the air of the air bubbles in the ink. When the thermoelectric unit is driven, heat is generated in the portion of the thermoelectric unit adjacent to the flow path unit, and this heat is transmitted successively through an ink supply port forming substrate, an ink chamber forming substrate and a nozzle plate, which are made from metallic members having more thermal conductivity than a ceramic member, and the heat is dissipated from the nozzle plate.
However, in Japanese Patent Application Publication No. 2001-146012, air bubbles are generated because the common ink chamber (common flow passage) is heated during ejection recording. If the ink supply port becomes covered by an air bubble, then ink is not supplied to the pressure chamber and an ejection failure may occur. Moreover, since the viscosity of the ink in the common ink passage becomes lower than the viscosity of the ink in the pressure generating chamber (pressure chamber), when ink is ejected from the nozzle, then the ink is liable to reflux into the common ink chamber, and hence the pressure in the pressure generating chamber may not be directed effectively towards ejection.